162 CHEMISTRY OF NATURAL WATERS. [IX. 



in the last determination derived from the magnesian sulphide, 

 leaving 1.110 .617 = .493 grammes due to the sulphide of 

 hydrogen in the water. If, however, the arsenious sulphide was 

 dissolved as sulpharsenite of sodium, AsS 8 ,3^"aS, in which 

 the sulphur ratio is 3 : 3, we have evidently .925 of sulphide 

 of arsenic derived from the sulphide of sodium in the water, 

 leaving only .185 to be formed by the sulphide of hydrogen. 

 Since, however, the water contains large proportions alike of 

 the chlorides of sodium, calcium, and magnesium, we may 

 suppose that there is a partition of bases, so that portions both 

 of alkaline and earthy sulphides may be present. The excess 

 of magnesian chloride would in any case produce the complete 

 decomposition, observed in boiling, into magnesia and sul- 

 phuretted hydrogen. 



Two questions then suggest themselves in the analysis of 

 this water; the first as to the relative proportions of sulphide 

 of hydrogen and the monosulphides of fixed bases, and the 

 second as to the base or bases of these fixed sulphides. To 

 resolve the first question, the following method suggests itself : 

 add to one measured portion of the water, at the spring, an 

 acid solution of terchloride of arsenic, by which the whole 

 amount of sulphide in the water may be determined. To 

 another portion add a neutral solution of chloride of zinc or 

 protochloride of iron, winch will precipitate the sulphur of 

 the fixed sulphides only, liberating the sulphide of hydrogen. 

 Having removed this by boiling, or by filtration, the insoluble 

 metallic sulphide might be treated with a mixture of a solution 

 of terchloride of arsenic and hydrochloric acid, by which means 

 its sulphur would be obtained as sulphide of arsenic, whose 

 weight, as compared with that from the former determination, 

 would show the quantities both of fixed and volatile sulphide 

 in the water. In connection with this, a determination of the 

 solvent power of the recent water for tersulphide of arsenic 

 would afford the means of solving the second question. 



For the analysis of the Both well water, the sulphate of lime 

 being determined by the amount of sulphuric acid, the chlorides 

 were calculated from the quantities of bases present, the sul- 



